Flutter 错误：类型 '(String, ItemPriority) => void' 不是类型 '(String, [ItemPriority]) => dynamic' 的子类型

Posted 2023-03-07

【中文标题】Flutter 错误：类型 \'(String, ItemPriority) => void\' 不是类型 \'(String, [ItemPriority]) => dynamic\' 的子类型

【英文标题】：Flutter error: type '(String, ItemPriority) => void' is not a subtype of type '(String, [ItemPriority]) => dynamic'Flutter 错误：类型 '(String, ItemPriority) => void' 不是类型 '(String, [ItemPriority]) => dynamic' 的子类型

【发布时间】：2020-10-31 17:33:11

【问题描述】：

我是 Flutter 新手，正在开发一个简单的待办事项列表应用程序。对于主页，我想要一个待办事项列表和一个添加新待办事项的按钮。点击“新建”按钮应该会打开一个窗口来输入待办事项的标题，并使用我的自定义单选按钮添加 1-5 的优先级。单击此窗口上的发送/提交按钮应将其添加到待办事项列表中（显示在 ListView 中）。

我收到此错误：类型 '(String, ItemPriority) => void' 不是类型 '(String, [ItemPriority]) => dynamic' 的子类型

它来自第 79 行“TodoInputWidget(this.newTodoItem)”，我试图追踪错误的原因，但我不确定我是否完全理解它。我找不到任何可以生成 ItemPrioritys 列表的地方。

我非常感谢您对此问题的任何见解！

这是我现在拥有的代码：

import 'package:flutter/material.dart';
import 'textInputWidget.dart';

void main() 
  runApp(MyApp());


enum ItemPriority  low, low_med, med, med_high, high 

extension ItemPriorityExtension on ItemPriority 
  RadioModel get radio 
    switch (this) 
      case ItemPriority.low:
        return new RadioModel(true, '1', Colors.green);
      case ItemPriority.low_med:
        return new RadioModel(true, '2', Colors.lightGreen);
      case ItemPriority.med:
        return new RadioModel(true, '3', Colors.yellow);
      case ItemPriority.med_high:
        return new RadioModel(true, '2', Colors.orange);
      case ItemPriority.high:
        return new RadioModel(true, '2', Colors.red);
      default:
        return new RadioModel(true, '3', Colors.yellow);
    
  


class TodoItem 
  String task;
  ItemPriority priority;

  TodoItem(this.task, this.priority);


class RadioModel 
  bool isSelected;
  String radioNumText;
  Color color;

  RadioModel(this.isSelected, this.radioNumText, this.color);


class MyApp extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return MaterialApp(
      title: 'Weekly ToDo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  


class MyHomePage extends StatefulWidget 
  @override
  _MyHomePageState createState() => _MyHomePageState();


class _MyHomePageState extends State<MyHomePage> 
  List<TodoItem> todos = [];

  void newTodoItem(String text, ItemPriority priority) 
    this.setState(() 
      todos.add(new TodoItem(text, priority));
    );
  

  @override
  Widget build(BuildContext context) 
    return Scaffold(
      appBar: AppBar(title: Text('Weekly ToDo')),
      body: Column(
        children: <Widget>[
          Expanded(child: TodoList(this.todos)),
          TodoInputWidget(this.newTodoItem),
        ],
      ),
    );
  


class TodoInputWidget extends StatefulWidget 
  final Function(String, [ItemPriority]) callback;

  TodoInputWidget(this.callback);

  @override
  _TodoInputWidgetState createState() => _TodoInputWidgetState();


class _TodoInputWidgetState extends State<TodoInputWidget> 
  String text;
  ItemPriority priority;
  CustomRadio radio = new CustomRadio(ItemPriority.med);

  bool selected = false;

  void createTodo(String text) 
    this.setState(() 
      widget.callback(text, radio.priority);
    );
  

  createTodoWindow(BuildContext context) 
    return showDialog(
        context: context,
        builder: (context) => SimpleDialog(
              title: Text('Create new task'),
              children: <Widget>[radio, TextInputWidget(this.createTodo)],
            ));
  

  @override
  Widget build(BuildContext context) 
    return GestureDetector(
      onTap: () 
        createTodoWindow(context);
      ,
      child: Container(
        alignment: Alignment.center,
        decoration: BoxDecoration(
          shape: BoxShape.circle,
          color: Colors.green,
        ),
      ),
    );
  


class TodoList extends StatefulWidget 
  final List<TodoItem> todoItems;

  TodoList(this.todoItems);

  @override
  _TodoListState createState() => _TodoListState();


class _TodoListState extends State<TodoList> 
  @override
  Widget build(BuildContext context) 
    return ListView.builder(
      itemCount: this.widget.todoItems.length,
      itemBuilder: (context, index) 
        var todoItem = this.widget.todoItems[index];
        return ListTile(title: Text(todoItem.task));
      ,
    );
  


class RadioItem extends StatelessWidget 
  final RadioModel item;
  RadioItem(this.item);

  @override
  Widget build(BuildContext context) 
    return Container(
      child: Text(item.radioNumText),
      decoration: BoxDecoration(
        shape: BoxShape.circle,
        color: item.color,
      ),
      alignment: Alignment.center,
    );
  


//ignore: must_be_immutable
class CustomRadio extends StatefulWidget 
  ItemPriority priority;

  CustomRadio(this.priority);

  @override
  _CustomRadiostate createState() => _CustomRadioState();


class _CustomRadioState extends State<CustomRadio> 
  List<RadioModel> priorityChoices = new List<RadioModel>();
  ItemPriority priority;

  @override
  void initState() 
    super.initState();
    widget.priority = priority;
    priorityChoices.add(ItemPriority.low.radio);
    priorityChoices.add(ItemPriority.low_med.radio);
    priorityChoices.add(ItemPriority.med.radio);
    priorityChoices.add(ItemPriority.med_high.radio);
    priorityChoices.add(ItemPriority.high.radio);
  

  @override
  Widget build(BuildContext context) 
    return ListView.builder(
      scrollDirection: Axis.horizontal,
      itemCount: priorityChoices.length,
      itemBuilder: (context, index) 
        return IconButton(
          onPressed: () 
            priorityChoices.forEach((element) 
              element.isSelected = false;
            );
            priorityChoices[index].isSelected = true;
            priority = ItemPriority.values[index];
          ,
          icon: RadioItem(priorityChoices[index]),
        );
      ,
    );
  

【参考方案1】：

替换函数;

  dynamic newTodoItem(String text, [ItemPriority priority]) 
     this.setState(() 
       todos.add(new TodoItem(text, priority));
     );
     return some.. or null;